Evaluation of different Ethiopian common bean, Phaseolus vulgaris (Fabaceae) genotypes for host resistance to the Mexican bean weevil, Zabrotes subfasciatus (Coleoptera: Bruchidae)

Common bean ( Phaseolus vulgaris L.) is amongst the most important grain legume crops in Africa in general, and Ethiopia in particular. The Mexican been weevil ( Zabrotes subfasciatus Boheman) heavily attacks the grain of common bean. A total of 300 common bean entries were subjected to a ‘no-choice’ test at Melkassa Agricultural Research Centre, Ethiopia, using a randomized complete block design with three replications, to evaluate for resistance to the Mexican bean weevil. Data on insect and seed traits were collected and a significant level ( P <0.01) of variation in all parameters measured was observed amongst genotypes. Relative resistance was recorded in landraces, improved genotypes and breeding lines, but the resistant genotypes, RAZ-11, RAZ-36, RAZ-2, RAZ-44, RAZ- 120, RAZ-40 and MAZ-203, showed consistently complete resistance, with zero index of susceptibility value. Two other promising entries were also identified from the breeding lines (SCR-11) and landrace collections (NC-16) of Ethiopia. Stratified ranking diagrams showed that accessions from different eco-geographical origins in Ethiopia and those with different colours showed different patterns of response to infestation. The Ethiopian bean breeding programme should take up the resistant genotypes for a comprehensive yield trial at the national level and direct release them as commercial varieties. The incorporation of bean weevil resistance genes into adapted varieties through backcross breeding techniques, supported with marker assisted selection, seems to be the best strategy not only in terms of time saving but also in terms of effectiveness and efficiency.